loplugin:cstylecast: deal with those that are (technically) const_cast

Change-Id: I35092571da3360038665b4d6bb993f92390f8d8d

include/editeng/svxrtf.hxx

@@ -391,7 +391,7 @@ public:
 
 inline const Color& SvxRTFParser::GetColor( size_t nId ) const
 {
-    ColorPtr pColor = (ColorPtr)pDfltColor;
+    ColorPtr pColor = pDfltColor;
     if( nId < aColorTbl.size() )
         pColor = aColorTbl[ nId ];
     return *pColor;